B20 contains "up to 20%" biodiesel in D1 or D2 base. So could always find a B10 blend, at the B20 pump. Sorta like E85 is never actually a true 85/15 ethanol blend. However biodiesel in general contains 70 times the lubrication factor of D1 or D2, yet zero Sulfur content. So any amount is a plus for new common rail pumps.
As for power and mileage, like Jason mentioned, the BTU's of straight B100 biodiesel is slightly less than what's known as D2 "Summer Blend" fuel. Kerosene is also lower BTU, and the reason ya might notice worse mileage in the winter vs summer on same vehicle.
D2 is blended with K1 to get D1, and keep diesel fuel from jelling in cold temps. And jet fuels blends are cut with gasoline for that same reason. In the winters, I would cut my personal blended B100 with 15% gasoline rather than Kero for same reasons. And ran that in many common rail setups. Then if a really cold week set in, cut that mixture further with D1 fuel, because high Biodiesel blends will always jell way above straight D1 or D2 temps, based on feedstock used. Getting over technical, but brings me to the key factor for bioD, the Cetane factor.
Based on just BTU figures, one would surmise all biodiesel fuels would get worse mileage than straight D2. Totally incorrect.. LOL. Besides better lubrication, biodiesel holds a couple other advantages over straight Diesel blends. Cetane is like the opposite of Octane, higher C equals easier ignition, as where higher octane is to prevent per-ignition, or knock. Diesels run on knock... B100 lights off at lower temps and burns way "cleaner and quicker" than D1 or D2 blends. And is main reason a diesel engine Knocks less and smokes less on B20 or any blend above that value. Running on high Bio blends, is same effect as adding 5deg of timing across the board.
Last factor, oxygenation of fuel. Biodiesel contains an extra oxygen molecule, like Methanol and Ethanol. Which while both have far less BTU than Gasoline, sure comes in handy for turning up the timing / power, at cost of 15-30% more fuel. Biodiesel is very similar to this, however that extra oxygen also cuts the shelf life, and makes it degrade and gum up fuel system parts if left laying open to the air for over 9 months by spec.. Bio-Degradable it is..
So now ya know all the main good and bad of Biodiesel. Yes it's also a great fuel system cleaner. Bottled under some brand names and sold at $20 a gallon.... Leave it set open for a couple years, it's also gonna stick your regular and injectors. However once ya understand the tricks, it's by far the best diesel performance additive ya can get.
Typically you will see better fuel mileage up to around 30-40% biodiesel on a stock diesel. Above that, the BTU limits come into play and numbers fall off again, at a cost of 5-10% mileage. However the cleaning and lube factor is probably gonna save ya in parts $$ down the road.. If your into racing, that Cetane # gonna help out way more than you expect with a little tweeking in the tuning. Ya just gained 3-5 deg of timing, without chance of busting a piston because the burn is so much smoother.. Then maybe toss in a little Nitro-methane, up that oxygen further, and now your cooking with some Outlaw Diesel Fuel.. Smell those fries a burning...
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